• Journal of Internet Computing and Services
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• v.25 no.4
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• pp.39-46
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• 2024

An API gateway is a high-availability component that provides a single entry point for API clients outside the cloud to connect with services inside the cloud. It has a high risk of creating bottlenecks and requires redeployment when services change. The Java language, in which several API gateways are implemented, announced technologies called GraalVM Native Image and Virtual Thread to overcome problems with deployment and operational performance. Applying these technologies to Java applications requires changes to the source code and deployment procedures. In this study, the performance of the API gateway was measured and analyzed when it operated based on GraalVM Native Image and Java Virtual Machine(JVM) and between Virtual Thread and Reactive thread processing methods. In this study, evaluation indicators were selected to evaluate deployment performance and operational performance, and the performance of the evaluation indicators was measured and evaluated in four environments.

• KSTLE International Journal
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• v.4 no.2
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• pp.56-59
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• 2003

Boron carbide thin coatings were deposited on silicon wafers by DC magnetron sputtering using a ${B}_4$C target with Ar as processing gas. Various amounts of methane gas (${CH}_4$) were added in the deposition process to better understand their influence on tribological properties of the coatings. Reciprocating wear tests employing an oscillating friction wear tester were performed to investigate the tribological behaviors of the coatings in ambient environment. The chemical characteristics of the coatings and worn surfaces were studied using X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). It revealed that ${CH}_4$addition to Ar processing gas strongly affected the tribologcal properties of sputtered boron carbide coating. The coefficient of friction was reduced approximately from 0.4 to 0.1, and wear resistance was improved considerably by increasing the ratio of ${CH}_4$gas component from 0 to 1.2 vol %. By adding a sufficient amount of ${CH}_4$(1.2 %) in the deposition process, the boron carbide coating exhibited lowest friction and highest wear resistance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.78-84
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• 2003

Boron carbide thin coatings were deposited on silicon wafers by DC magnetron sputtering using a $B_4C$ target with As as processing gas. Various amounts of methane gas $(CH_4)$ were added in the deposition process to better understand their influence on tribological properties of the coatings. Reciprocating wear tests employing an oscillating friction wear tester were performed to investigate the tribological behaviors of the coatings in ambient environment. The chemical characteristics of the coatings and worn surfaces were studied using X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). It revealed that $CH_4$ addition to As processing gas strongly affected the tribologcal properties of sputtered boron carbide coating. The coefficient of friction was reduced approximately from 0.4 to 0.1, and wear resistance was improved considerably by increasing the ratio of $CH_4$, gas component from 0 to $1.2\;vol\;\%$. By adding a sufficient amount of $CH_4\;(1.2\%)$ in the deposition process, the boron carbide coating exhibited lowest friction and highest wear resistance.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2048-2050
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• 1998

An uninterruptible power supply(UPS) with parallel operation is used to increase the power capacity of the system or to secure higher reliability at critical loads. In the parallel operating system composed of the multiple UPSs, load-sharing, i.e. current balance control between them is key technique. Because of its low impedance and quick response characteristics, inverter output current changes very rapidly and thereby easily researches an overload condition. The difference between total load current divided by number of operating inverters and its own current is detected as unbalanced current. Then frequency and voltage are controlled to minimize the active component and the reactive component. A good performance of the proposed load-sharing technique is verified by experiments in the parallel operating system with two 40kVA UPSs.

• Journal of the Korean Applied Science and Technology
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• v.20 no.2
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• pp.87-93
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• 2003

Two-component polyurethane flame retardant coatings (ATTBC) were prepared by blending polyisocyanate (TDI-adduct) with ATTBs mentioned at the previous paper. Most of the physical properties of the flame retardant coatings were comparable to those of non-flame retardant coatings. Especially, the hardness, impact resistance, and accelerated weathering resistance were remarkably improved with the increase of the content of 1,4-butanediol. Coatings containing 10 and 15 wt% 1,4-butanediol, ATTBC-10C and ATTBC-15C, were not flammable in vertical flame-retardancy test. Their char area recorded 1.1${\sim}$11.6 $cm^2$ in 45$^{\circ}$ eckel burner method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.103-110
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• 1998

The modeling of load characteristics is a difficult problem because of uncertainty of load. This research uses artificial neural networks which can approximate nonlinear problem to represent load characteristics. After the selection of typical load, active and reactive power for the variation of voltage and frequency is obtained from experiments. We constructed and learned ANN based on these data for component load identification. The learned ANN identified load characteristics for other voltage and/or frequency variation. In addition, the results of component load identification are presented to demonstrate the potentiality of the proposed method.method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.64-72
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• 1999

The fictitious power theory in time domain is very easy to understand, but power analyzing speed of active power is increased, because power is analyzed using signal tedmiques based on the corre1ation between voltage and current wavefonns. Also, conventional methods in time/frequency domain to evaluate the correlation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundarrental reactive component and distorted component of nonlinear loads current. This trethod has excellent perfonnance, but can not evaluate the characteristics of nonlinear load current whether It is inductive or capacitive. Therefore, To overcorre problems trentioned previously, this paper deals with the simple average power theory and the modified 3-D current coordinates for evaluating the compensation perfonnance of active power filters. To confirm the validity, active power filter simulator is developed using C-language. From the simulation, results are discussed their utility.tility.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.1-10
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• 2015

This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.229-237
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• 1992

Series system reliability analysis of non-reactive contaminant transport is performed in a two dimensional horizontal domain with two different limit state functions: (1) concentration threshold and (2) exposure time threshold. The transient source transport model is combined with the system reliability model to evaluate the probability that a specified maximum concentration at a node of interest would be exceeded or that a moderate concentration would exceed some exposure limit over a given period of time. The results give probabilities of exceedence greater than probability of each component and they tend to be dominanted by the component with larger probability. Transverse dispersivity turns out to be an important parameter in addition to hydraulic conductivity in a two-dimensional contaminant transport model with transient source. System sensitivity is found to reflect the corresponding sensitivity of both components, with the component with larger probability having a greater influence.

• Molecules and Cells
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• v.38 no.12
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• pp.1054-1063
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• 2015

Mitochondria play a crucial role in eukaryotic cells; the mitochondrial electron transport chain (ETC) generates adenosine triphosphate (ATP), which serves as an energy source for numerous critical cellular activities. However, the ETC also generates deleterious reactive oxygen species (ROS) as a natural byproduct of oxidative phosphorylation. ROS are considered the major cause of aging because they damage proteins, lipids, and DNA by oxidation. We analyzed the chronological life span, growth phenotype, mitochondrial membrane potential (MMP), and intracellular ATP and mitochondrial superoxide levels of 33 single ETC component-deleted strains during the chronological aging process. Among the ETC mutant strains, 14 ($sdh1{\Delta}$, $sdh2{\Delta}$, $sdh4{\Delta}$, $cor1{\Delta}$, $cyt1{\Delta}$, $qcr7{\Delta}$, $qcr8{\Delta}$, $rip1{\Delta}$, $cox6{\Delta}$, $cox7{\Delta}$, $cox9{\Delta}$, $atp4{\Delta}$, $atp7{\Delta}$, and $atp17{\Delta}$) showed a significantly shorter life span. The deleted genes encode important elements of the ETC components succinate dehydrogenase (complex II) and cytochrome c oxidase (complex IV), and some of the deletions lead to structural instability of the membrane-$F_1F_0$-ATP synthase due to mutations in the stator stalk (complex V). These short-lived strains generated higher superoxide levels and produced lower ATP levels without alteration of MMP. In summary, ETC mutations decreased the life span of yeast due to impaired mitochondrial efficiency.